functional anatomy Flashcards
Identify the correct order, from largest to smallest, the terms that relate to that of a skeletal muscle structure.
Fascicle, muscle fibre, myofibrils, myofilament
Identify and describe the theory which explains the process that causes sarcomeres to shorten during concentric contraction.
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The Sliding Filament Theory
calcium is released and enters the sarcomere
myosin is stimulated to reach for actin
myosin attached to actin filaments creating a cross bridge
breakdown of ATP releases energy to stimulate cross bridges
myosin pulls on actin
sarcomere shortens as actin filaments move closer together
actin and myosin overlap causing I band and H zone to disappear
calcium leaves the sarcomere
This causes the actin to move into the centre of the sarcomere, shortening the myofibril and causing the actin and myosin filaments to be almost fully overlapped when in a fully contracted position. (1 mark)
As each sarcomere shortens, so does the total length of each muscle fibre.
explain how he will be able to be fully contracted one moment, then be able to continue to run at high speed.
Once the contraction is finished, the myosin releases it’s grip on the actin. (1 mark)
The release of this grip, coupled with elastic energy stored in the tendons, allows the sarcomere and subsequent muscle fibre to relax and lengthen to it’s resting length, ready for another contraction. (1 mark)
Using your knowledge of the neuromuscular system, explain why the individual failed in their initial attempt to lift the bar and describe what they would have done differently on their second occasion to allow them to lift the bar successfully.
Failed due to 2 different reasons
Didn’t send strong enough message from brain to recruit the right type of fibres (1 mark)
Didn’t send enough messages (frequency) to recruit increased number of motor units (1 mark)
On the second occasion
Would have sent stronger message from the brain to recruit more powerful motor units (1 mark)
Would have increased the frequency/rate of firing to recruit more fibres (1 mark)
Describe how the velocity of the contraction could affect the amount of force produced by the athlete.
Muscle force is large when slow velocity (1 mark)
Muscle force is moderate when moderate velocity (1 mark)
Muscle force is low when fast velocity (1 mark)
On your own piece of paper, draw a fully-labelled graph to represent the relationship between the velocity of muscle contraction and the amount of force produced in a concentric contraction. Provide a description of the relationship.
Any one of: (1 mark)
States the amount of force produced by a muscle depends upon the velocity of muscle contraction
Saying either - High velocity = low force / Slow velocity = high force
Discusses myosin-actin cross bridges
b)
On your own piece of paper, draw a fully-labelled graph to represent the relationship between the length of a muscle and the amount of force exerted in a concentric contraction. Provide a description of this relationship.
Force labeled on Y axis (1 mark)
Muscle length labeled on X axis (1 mark)
Correct curve drawn (1 mark)
Any one of: (1 mark)
States how muscle force depends upon the length of a muscle
Identifies that maximum force is produced when there is optimal overlap of actin and myosin.
A muscle is able to generate greatest force at a starting length that is closest to the resting/midrange/optimal length
Less force is generated by a muscle that has a starting length that is stretched (l
Identify three (3) characteristics of Type IIb muscle fibres
- Very Fast contraction time
- Very large size of motor neuron
- Low resistance to fatigue
- Used for short term anaerobic activities
- Very high force production
- Low capillary density
- Low oxidative density
- Low mitochondria density
Define the ‘All or Nothing’ principle and apply your knowledge of muscle fibre recruitment to the different skills pictured below
When a motor unit is stimulated, all the muscle fibres within that unit contract with 100% force (1 mark)
Netball goal shot - low threshold required and recruits mainly slow-twitch fibres (1 mark)
Golf drive - High threshold required and recruits fast-twitch and slow-twitch fibres (1 mark)
name the contractile component of skeletal muscle and identify it’s composite proteins.
The Sarcomere is the smallest contractile unit in skeletal muscle. (1 mark)
It is made up of Actin and Myosin proteins. (1 mark)
b)
Explain using Sliding Filament Theory, how the muscles of the forearm facilitate a ‘grip’ on the bar.
The message is received by the muscle from Motor Neuron.
19
The Sliding Filament Theory
calcium is released and enters the sarcomere
myosin is stimulated to reach for actin
myosin attached to actin filaments creating a cross bridge
breakdown of ATP releases energy to stimulate cross bridges
myosin pulls on actin
sarcomere shortens as actin filaments move closer together
actin and myosin overlap causing I band and H zone to disappear
calcium leaves the sarcomere
The shortening of the muscle belly, causes the bones of the fingers to wrap around the bar, creating the grip. (1 mark)
1 mark for Actin/Myosin link. 1 mark for Shortened sarcomere. 1 mark for consequence on muscle length. 1 mark for relating to grip.
Epimysium
Connective tissue around whole muscle. Transfers tension to bone to create movement
endomysium
Connective tissue around each muscle fibre
perimysium
Connective tissue around the fascicle
z lines
Found at either end of the sarcomere. The Z lines of a sarcomere come closer together in concentric contract and spread further apart as the muscle relaxes or in an eccentric contraction.
ACTIN
ACTIN
ACTIN
The thin protein filament attached to the Z line. Cross bridges on the myosin attach to the actin when stimulated by the release calcium to create movement. Actin filaments are attached the Z line and pull the Z line towards the midline of the sarcomere in a concentric contraction.
MYOSIN
The thick protein filament which contain crossbridges . The myosin cross bridges attach to the actin when stimulated in the presence of calcium.
CROSSBRIDGES
CROSSBRIDGES
Tiny projections on myosin filaments that attach on the actin filaments, pulling the actin filaments towards the mid line of the sarcomere, making the H zone shorten or disappear which shortens the sarcomere shortening the myofibril and creating movement (concentric contraction)
The Sliding Filament Theory
calcium is released and enters the sarcomere
myosin is stimulated to reach for actin
myosin attached to actin filaments creating a cross bridge
breakdown of ATP releases energy to stimulate cross bridges
myosin pulls on actin
sarcomere shortens as actin filaments move closer together
actin and myosin overlap causing I band and H zone to disappear
calcium leaves the sarcomere
The Nervous System
3 key functions;
Through sense organs and sensory nerves, it receives information about changes in the body and the environment and sends this information to the spinal cord and brain.
Brain determines suitable response
Brain sends commands to muscles to
carry out selected response
In order to contract , muscle fibres must be stimulated by nerve or electrical impulses sent via motor neurons or nerves.
For this to take place;
A message is sent from the brain, in the form of an action potential (electrical impulse), down the spinal cord
The action potential is detected by the dendrites of a motor neuron which send the information to the cell body
The cell body directs the information down the axon to the motor end plate (attached to targeted muscle)
The action potential is delivered to the muscle which is innervated as long as the signal / stimulus / impulse is strong enough
ISOTONIC force
ISOKINETIC force—
ISOMETRIC contraction
Muscle changes length working against a constant load eg bicep curl, bench press etc.
An isokinetic force results in a change in muscle length against a varying load. but requires expensive specialised equipment to
If the muscle length does not change, then an isometric contraction or force is being applied.
The force produced by a muscle can be increased in 2 ways;
Increasing the number of motor units recruited by increasing the size of the stimulus. Increasing the number of motor units used in generating force will increase the size of the force generated.
Increasing the rate at which impulses are sent to the motor unit resulting in the motor unit firing repeatedly to increase the force generated
FORCE – VELOCITY
Definition
Force – Velocity describes the relationship between force production and the velocity of movement
FORCE – LENGTH
Definition
Relates to the amount of muscle force that can be produced at varying muscle lengths
